Characterization of Pre-Antibiotic Era Klebsiella pneumoniae Isolates with Respect to Antibiotic/Disinfectant Susceptibility and Virulence in Galleria mellonella

Abstract

ABSTRACTThe EGD Murray collection consists of approximately 500 clinical bacterial isolates, mainlyEnterobacteriaceae, isolated from around the world between 1917 and 1949. A number of these “Murray” isolates have subsequently been identified asKlebsiella pneumoniae. Antimicrobial susceptibility testing of these isolates showed that over 30% were resistant to penicillins due to the presence of diverseblaSHVβ-lactamase genes. Analysis of susceptibility to skin antiseptics and triclosan showed that while the Murray isolates displayed a range of MIC/minimal bactericidal concentration (MBC) values, the mean MIC value was lower than that for more modernK. pneumoniaeisolates tested. All Murray isolates contained the cation efflux genecepA, which is involved in disinfectant resistance, but those that were more susceptible to chlorhexidine were found to have a 9- or 18-bp insertion in this gene. Susceptibility to other disinfectants, e.g., H2O2, in the Murray isolates was comparable to that in modernK. pneumoniaeisolates. The Murray isolates were also less virulent inGalleriaand had a different complement of putative virulence factors than the modern isolates, with the exception of an isolate related to the modern lineage CC23. More of the modern isolates (41% compared to 8%) are classified as good/very good biofilm formers, but there was overlap in the two populations. This study demonstrated that a significant proportion of the MurrayKlebsiellaisolates were resistant to penicillins before their routine use. This collection of pre-antibiotic era isolates may provide significant insights into adaptation inK. pneumoniaein relation to biocide susceptibility.